Salinity Intrusion and Seasonal Water Quality Variations in the Tidal ...

taught us to value fresh water more realistically. Figure 1.2 shows the global water use
pattern.
1.2 Availability offresh water for human activities
The immediate concern of human beings is the availability of fresh water at
terrestrial patches inhabited by humans. The fresh water distribution over our globe is
uneven and quite unrelated to population spread or economic development. Figure 1.3
depicts the distribution ofwater resources. Due to rapid population growth, the potential
availability ofwater decreased from 12900 M 3 per capita per year in 1970 to 9000 M 3 in
1990 and less than 7000 M 3 in 2000. Also, it is estimated that three billion people will be
in the water scarcity category of 1700 M 3 per capita per year by 2025 (UNEP, 2002). In
India the water availability in the first fifty years ofindependence fell by 62 % from 6008
M 3 in 1947 to 2266 M 3 in 1997 (Fig 1.4). If business continues as usual it is going to
fall from 2266 to 750 m 3 in the next 50 years. Among the countries projected to fall into
the water stress category before 2025 is India. By 2025, India's population is expected to
exceed 1.4 billion under the UN's medium projection and hence, the chronic water
scarcity that already plagues many regions of the country is all but certain to intensify
(World Water Resources Institute, 1993). By that time India's per capita availability of
water will fall below 1000M 3 per year (Shanna, 2003). This being the shape ofthings to
come it is the duty of the state and the people to preserve the physical, chemical and
biological integrity ofthe nation's water sources. Integrity ofthe water body is defined as
the ability of the water body's ecological system to support and maintain a balanced,
integrated and adaptive community of organisms comparable to that of the natural biota
ofthe region (Novotny,. et al., 2004). Table 1.1 illustrates the global distribution ofwater.
2